1. Industrial Field of the Invention
The present invention relates to a dome shaped roof structure, and in particular, relates to a dome shaped roof structure which is suitable for a stadium for indoor athletic sports.
2. Related Art
Recently, a large-scale fixed dome shaped roof structure has been adopted in the construction of stadiums for indoor athletic sports. A steel truss structure, a cable structure or the like is generally known as a fixed dome shaped roof structure.
The steel truss structure is organized in the form of a double layer truss dome (a double layer space frame) which has a space truss structure comprising connected steel members to ensure relatively good structural stability, and a single layer truss dome (a single layer space frame) which has a plane truss structure comprising connected steel members as shown in FIG. 23. However, construction of the double layer truss dome is costly and requires a long time in order to assure good structural stability of the roof. Therefore, the single layer truss dome structure 1 is often adopted in order to lighten the weight thereof and to reduce the cost and length of construction thereof.
In contrast, the cable roof structure of a fixed dome shape, as shown in FIG. 24, comprises multiple cables 2 and 3 forming a plurality of upper and lower chord members, and a plurality of strut members 4 which are each vertically supported by the cables 2 and 3. The cables 2 to which high tension is introduced in the external direction are bound with a compression ring 5 along the bottom of the dome, i.e. the bottom peripheral edge of the dome shaped roof.
The single layer truss dome structure 1 has a problem with respect to the buckling strength of the dome construction members. For example, the dome construction members are apt to easily collapse from offset load of snow deposited on the dome shaped roof or the like. The bottom peripheral edge of the dome requires a strong tension ring 6 in order to resist the large thrust which is applied to the bottom border of the dome in the direction indicated by the arrow A in FIG. 24. Consequently, the construction costs including the tension ring 6 and the tension ring supporting means are greatly increased.
Since the cable roof structure is flexible, the above cable roof structure comprising flexible cables 2 and 3, requires a large prestress to the cable 2 in order to increase the structural stability thereof. Therefore, the border of the structure requires a strong compression ring 5 in order to resist the large thrust applied in the direction indicated by the arrow B in FIG. 24. In contrast with the case of the single layer truss dome structure 1, the construction costs including the tension ring 6 and the tension ring supporting means are greatly increased.